In recent years, many proposals have been made for the use of the clean energy hydrogen as an energy source.
To produce hydrogen, the general technique used has been steam reforming using a hydrocarbon fuel. Further, in recent years, it has been considered to obtain hydrogen from water by the splitting of water, in particular the splitting of water using solar light energy. When obtaining hydrogen by the splitting of water, the product obtained sometimes becomes a mixture of hydrogen, oxygen, and water. In this case, to obtain the hydrogen, it is necessary to separate and take out only this hydrogen from this mixture.
In relation to this, Japanese Unexamined Patent Publication (A) No. 2001-213608, Japanese Patent Publication (A) No. 10-218601, International Patent Publication WO99/38215, and Japanese Unexamined Patent Publication (A) No. 2008-075097 propose water-splitting apparatuses using water to catalytically or electrolytically split water wherein the hydrogen and oxygen are generated at separate electrodes and thereby the hydrogen and oxygen are separately recovered.